RE: [PATCH v10 04/30] x86/resctrl: Optimize cpumask_any_housekeeping()

[Shaopeng Tan (Fujitsu)]

Hello James,

> From: "Yury Norov [NVIDIA]" <yury.norov@xxxxxxxxx>
> 
> With the lack of cpumask_any_andnot_but(), cpumask_any_housekeeping()
> has to abuse cpumask_nth() functions.
> 
> Update cpumask_any_housekeeping() to use the new cpumask_any_but()
> and cpumask_any_andnot_but(). These two functions understand
> RESCTRL_PICK_ANY_CPU, which simplifies cpumask_any_housekeeping()
> significantly.
> 
> Tested-by: James Morse <james.morse@xxxxxxx>
> Reviewed-by: James Morse <james.morse@xxxxxxx>
> Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
> Signed-off-by: Yury Norov [NVIDIA] <yury.norov@xxxxxxxxx>
> Signed-off-by: James Morse <james.morse@xxxxxxx>
> ---
>  arch/x86/kernel/cpu/resctrl/internal.h | 28 +++++++-------------------
>  1 file changed, 7 insertions(+), 21 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h
> b/arch/x86/kernel/cpu/resctrl/internal.h
> index eaae99602b61..25b61e466715 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -47,30 +47,16 @@
>  static inline unsigned int
>  cpumask_any_housekeeping(const struct cpumask *mask, int exclude_cpu)
> {
> -	unsigned int cpu, hk_cpu;
> -
> -	if (exclude_cpu == RESCTRL_PICK_ANY_CPU)
> -		cpu = cpumask_any(mask);
> -	else
> -		cpu = cpumask_any_but(mask, exclude_cpu);
> -
> -	/* Only continue if tick_nohz_full_mask has been initialized. */
> -	if (!tick_nohz_full_enabled())
> -		return cpu;
> -
> -	/* If the CPU picked isn't marked nohz_full nothing more needs doing.
> */
> -	if (cpu < nr_cpu_ids && !tick_nohz_full_cpu(cpu))
> -		return cpu;
> +	unsigned int cpu;
> 
>  	/* Try to find a CPU that isn't nohz_full to use in preference */
> -	hk_cpu = cpumask_nth_andnot(0, mask, tick_nohz_full_mask);
> -	if (hk_cpu == exclude_cpu)
> -		hk_cpu = cpumask_nth_andnot(1, mask,
> tick_nohz_full_mask);

It seems that the cpumask_nth_andnot() function is no longer used anywhere,
so it's better to remove it from ./include/linux/cpumask.h.

Best regards,
Shaopeng TAN

> +	if (tick_nohz_full_enabled()) {
> +		cpu = cpumask_any_andnot_but(mask, tick_nohz_full_mask,
> exclude_cpu);
> +		if (cpu < nr_cpu_ids)
> +			return cpu;
> +	}
> 
> -	if (hk_cpu < nr_cpu_ids)
> -		cpu = hk_cpu;
> -
> -	return cpu;
> +	return cpumask_any_but(mask, exclude_cpu);
>  }
> 
>  struct rdt_fs_context {
> --
> 2.39.5